(1) Field of the Invention
The present invention relates to a telephone system and, in particular, to a calling system from a party for a busy party.
(2) Description of the Prior Art
In a conventional telephone system, a plurality of telephone sets are connected to exchange equipment through two-wire or four-wire telephone lines. Any one of the telephone sets can be connected to another one through the exchange equipment. When two telephone sets are connected to each other through the exchange equipment, the exchange equipment rejects a call from another telephone set for connection with any one of the busy telephone sets and sends out a, so called, busy tone to the calling telephone set.
In actual use of the telephone system, when a person sometimes desires to give information to a party communicating with another party without interruption of the communication and without the information being transmitted to the other party, he must physically come to the party to orally convey the information or to show him a memorandum having the information. However, it is inconvenient for a remote person physically to come to the party.
A conference call system is known and used in the prior art wherein several telephone sets can be called by a telephone set and those telephone sets are connected to one another for enabling conversation among them.
In the conference call system, a call for any one of the busy parties from a third party is also rejected.
As a system for enabling a calling party to be connected to a called busy party, a call waiting system is known in the prior art. During a conversation between a first party and a second party, a ringing signal is sent out to the first party in response to a call for the first party from a third party. When the first party effects a hooking operation, the first party is connected to the third party in place of the second party, while the second party is held. However, in the system, the call from the third party cannot be completed in the absence of the hooking operation of the called first party. Further, the connection between the first and third parties results in a temporary interruption of the conversation between the first and second parties.